This invention relates to antennas of the type having a parabolic reflector element for concentrating microwave radiation, transmitted from a feed arrangement located at the focal point of the reflector, into a collimated microwave beam. More particularly, the invention relates to feed arrangements for such antennas.
Parabolic reflector antennas are used for directional radio and satellite transmission. The parabolic reflector can be a grid structure or a solid structure.
The reflectors of the antennas are normally illuminated by feed arrangements in the form of either a buttonhook feed horn or a dipole radiator with a subreflector. Horn fed antennas are normally used for frequencies above 3 GHz, and dipole radiator arrangements are used for frequencies below 3 GHz.
Above 3 GHz, required dimensions of the horn feed structure of a horn fed antenna are such that the minimum parabolic reflector size is typically limited to about 1.8 meters. Below this reflector size the antenna suffers aperture blockage which degrades the radiation pattern of the antenna and renders it less efficient.
Known dipole feed arrangements are commonly made from discrete machined metallic components, and moreover, require a separate balun arrangement.